Lemongrass Shrimp Soup with Spaghetti Squash

Preheat oven to 375°. Pierce squash all over with a knife to vent. Roast on a rimmed baking sheet, turning every 20 minutes, until tender (knife will easily slide through), 60–90 minutes.

Let cool slightly. Halve lengthwise and scoop out seeds; discard. Scrape flesh with a fork to remove in long strands. Spread out on paper towels to drain.

Meanwhile, peel and devein shrimp, reserving shells. Place shrimp in a medium bowl; cover and chill until ready to use. Heat oil in a medium pot over medium-high. Cook shrimp shells, stirring occasionally, until bright pink and browned in spots, about 30 seconds. Add scallions, lemongrass, ginger, and garlic, reduce heat to medium, and cook, stirring occasionally, until softened, about 3 minutes. Add broth and bring to a boil. Reduce heat and simmer until flavors marry and come together, about 30 minutes. Strain through a fine-mesh sieve into a clean medium saucepan; discard solid.

Bring broth to a boil. Reduce heat, add chilled shrimp, and simmer until shrimp are cooked through, about 2 minutes; season with salt.

Divide squash among bowls and ladle shrimp and broth over to cover. Top with cilantro and chiles and serve with lime wedges for squeezing over.